When he was training at the legendary Chicago improv theater Second City, Chris Farley once confronted a colleague who was being cold to him and asked, “Why don’t you like me?”

“It’s not that I don’t like you,” recalls director Cheryl Sloane in the new oral history of the training grounds that bred the likes of Farley, Stephen Colbert, Bill Murray, Tina Fey and Mike Myers. “It’s that I don’t want to be close to you because you’re killing yourself.”

Legendarily competitive, crawling with substance abuse and featuring manic genius often bordering on the psychotic, Second City is notorious for oversized personalities whose behavior often repulsed as much as it inspired. And while this book is chock full of comedy, it’s the stories of human waste that are most unforgettable.

Sometimes actual human waste, in fact. One story about Farley is about his “s— sock.” Because he apparently didn’t own toilet paper, he would relieve himself with this item of clothing and then was later seen wearing it. “He had no off switch,” said cast member Joe Liss. “We had an off switch. Most of us.”

Farley’s biggest comedy hero John Belushi also didn’t have an off switch. Farley was obsessed with Belushi, and even talked about wanting to “flame out” like his idol, which sadly he did.

Remembers Liss of Farley, “We were all in the pot with him. We were all going out drinking. We were smoking dope, snorting cocaine. He wasn’t alone. Oh, my God, no. But unfortunately, he didn’t know when to quit.”

By comparison, later success stories such as Tina Fey and Stephen Colbert show what happens when the manic performing energy is channeled almost purely into the art itself.

Because Colbert improvised so much on stage, he said he found himself doing it in real life, too. When some gorgeous woman at a club seemed unapproachable, Colbert pretended he was simply making up a new scene where he played a modeling scout.

“I said, ‘I bet like this [snaps fingers], I could get that girl to talk to me,’ ” Colbert recalls. “I said . . . ‘I just want to talk to you about your look.’ She came over and gave me the time. And I walked back over and said, ‘There, I did it.’ . . . In sweatpants. And I don’t have the greatest physique.”

Perhaps the tameness of these later stories is because, as Second City’s vice president Kelly Leonard observes, “The drug culture that existed when I first started here began dying off as people died.”